Perception of Airborne Chemosensory Cues by Sea Turtles

For sea turtles, an ability to locate nesting regions and foraging areas is vital. Turtles probably rely on several sensory cues to find these areas, some of which may be chemical in nature. Sea turtles can detect chemical cues in water, and because they surface to breathe, they potentially also have access to olfactory cues in air. To determine whether sea turtles can detect airborne chemical cues, loggerhead turtles (Caretta caretta ) were exposed to air that had passed across a cup containing their food or distilled water. Food odors elicited increased searching behavior only after turtles surfaced to breathe, implying that turtles could detect airborne food cues.;During long-distance migrations, many sea turtles feed on invertebrates that are abundant in productive ocean regions. An ability to distinguish these regions from other areas might be adaptive. The volatile compound dimethyl sulfide (DMS) accumulates in the air above productive areas, and might serve as an indicator of high prey density for turtles. To determine whether turtles perceive DMS, loggerheads were exposed to air scented with DMS, distilled water, or several non-oceanic odors. Turtles exposed to DMS spent more time at the water surface than did turtles exposed to other odors, implying that turtles can detect DMS and might use this odor as a foraging cue.;An ability to detect land masses from some distance away, and to distinguish coastal areas from the open sea, might also be adaptive for turtles. In additional experiments, turtles exposed to coastal mud were shown to spend more time at the water surface than did control turtles, suggesting that they can perceive an odor associated with land.;Turtles navigating to natal areas have been hypothesized to rely on a combination of magnetic and olfactory cues. To determine whether such a strategy is plausible for turtles that nest on islands, I modeled airborne and waterborne odor plumes emanating from Ascension Island (a remote island in the South Atlantic) and overlaid these on maps of magnetic intensity. Results indicated that turtles can plausibly reach the vicinity of the island using magnetic cues, then locate the island using chemical cues.